1. Field of the Invention.
The present invention relates generally to capacitive sensors and, more particularly, to a capacitive sensor element in which the primary parts thereof are in direct contact, thus permitting construction of a rugged sensor that is particularly useful in harsh environments.
2. Background Art.
Capacitive sensors of the position sensing type typically comprise two, conductive, members disposed for relative movement therebetween separated by a dielectric material, with the relative position of the conductive members determining the capacitance of the sensor. In one particular field of application, that of automotive vehicles, such sensors can be useful, for example, as input devices for automatic leveling systems and throttle position input devices for electronic engine controls.
Conventionally, position sensors for such applications include potentiometers with sliding contacts and capacitive devices in which the dielectric material is air or a plastic. The former suffer the disadvantage that they are subject to corrosion and wear and cannot easily tolerate dirty environments. The latter suffer the disadvantage that, when the dielectric is air, the device is subject to erratic output, due to vibrations (causing the spacing to change), temperature changes, and dirty conditions.
In general, desirable characteristics of improved capacitive sensors elements include a large change in capacitance for a small change in position, a small loss factor, high electrical resistance, a high electrical breakdown strength, as well as special characteristics of the material to permit certain constructions which make possible ruggedized construction.
Accordingly, it is a principal object of the present invention to provide a capacitive sensor element which can be ruggedly constructed.
A further object of the invention is to provide such a sensor element which is relatively insensitive to temperature changes.
An additional object of the invention is to provide such a sensor element which is insensitive to vibration.
It is another object of the invention to provide such a sensor element which can be used in dirty environments.
Other objects of the present invention, as well as particular features and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.